The long-term objectives of this competing renewal are to apply conditional gene manipulation techniques developed for mice to the analyses of molecular, cellular, and neuronal ensemble mechanisms underlying hippocampus-dependent learning and memory. Using the molecular genetic methods developed in this laboratory, mouse strains will be generated in which the gene encoding the a isoform of Ca2+/calmodulin-dependent protein kinase-II (CaMKII), or the g or B isoform of protein kinase C (PKC) is deleted (knocked out) specifically and separately in CAl or CA3 pyramidal cells of the hippocampus. Several transgenic mice will be generated in which the CaMKII inhibitor protein (CaMKII-IN) is overexpressed specifically in CAl or CA3 pyramidal cells, or a dominant negative form of Ca2+/calmodulin-dependent protein kinase-IV (dnCaMKIV) is overexpressed in the forebrain. The issue of whether expression of long term potentiation (LTP) at Schaffer collateral CAl synapses is based on a pre- or postsynaptic mechanism will be examined by subjecting the CAl- or CA3- specific CaMKII knockout, PKC knockout and CaMKII-IN transgenic mice to electrophysiological analysis of brain slices. This study will also examine whether LTP underlies learning and memory by analyzing the CAl-specific alphaCaMKII knockout, CAl-specific CaMKII-IN transgenic, and the forebrain-specific CaMKIV transgenic mice with electrophysiological and behavioral methods. Furthermore, the role of CaMKIV in different phases of the mnemonic process, namely acquisition, consolidation, and retrieval of memory, will be assessed by analyzing dnCaMKIV transgenic mice in which the level of expression of dnCaMKIV can be reversibly controlled. It is proposed to identify and characterize genes that are activated in the CAl region upon the formation of a long term memory by combining mouse genetics technology developed in this laboratory with DNA chip and DNA microarray technologies. Finally, it is proposed to study roles of CA3 NMDA receptors and the CA3 recurrent network in learning and memory, and in the formation of memory representation in the hippocampus by creating CA3-specific NMDA receptor knockout mice and subjecting them to a variety of memory tasks and to in vivo multielectrode recordings, respectively. The knowledge gained from these studies will constitute the basis for developing diagnostic and therapeutic methods for neurodegenerative diseases such as Alzheimer's disease and Huntington's disease as well as for the development of learning enhancement methods.